Potentiometer



. H. S. SCOTT l POTENTIOMETER Filed June 13 1923 2 Sheets-'Sheet 1 wml m-LH

June 3, 1.924. '1,496,745

H.l s. scoTT POTENTIOMETER June 13, 1925 2 Sheets-Sheet 2 IVENTOR Hoy? 5. .SCOTT oyl ATTORNEY which the following is a specification.

`zen ofithe United States, 'residing at Cleveland, the county of Cuyahoga and State vin accordance with a logarithmic curve yin drawings, in which:

elevation of the Patented-June 3, 1,924.`

UNITED STATES PATENT, OF

non* s.- scor'r, or CLEVELAND, omo. rorENTIomigrEn.

FICE.

Application led June 13, 1923. Serial No. 645,117.

To all-whom t may` concern.'

cuit employing my potentiometer' and Fig. Be 1 known that I, HoYT S. Scocl'r, a citib 9, illustrates one application of tion wherein to re of Ohio, have invented a certain new and ity o useful Improvement in a Potentiometer, of fr grid potential fora pluralelectrontubes functioning as a radio equency amplifier in a radio receiving apparatus. y invention relates broadl to apparatus for varying the resistance o! an electrical circuit, and mo e particularly to a constructionlof potentiometer.

One of vthe objects of my inventionis to provide a construction of potentiometer whereby the resistance of its associated electrical circuit may be varied by small and tion may be mounted. secured by any suitable means such as 3 to the panel and carries an insulated band 4. This band may be semi-circular in form as represented in Fig. .1,

gradualy increasing or diminishing increcular as represented at 6 in Fig. i4." The ments o adjustment. band 4 in Fig. l is secured to the support 2 Another object of the invention is to prob vide a potentiometer construction whereby the resistance of the electrical circuit associated with the potentiometer may be Varied by small increments of adjustment near either end of the potentiometer and largery increments of adjustment intermediate the ends of the potentiometer.

A further object of the invention is to provide a variable resistance device operative to control the resistance of an electrical circuit in accordance with a logarithmic law.

A still further object of the invention is to provide a potentiometer construction in which the variation in resistance takes place y means of screws 5 and 7 which serve as binding posts at 12 and 14 for the opposite ends of the potentiometer. These screws pass through the band 4 and lated from the support 2. The band 4 is of a substantial width at its central section and throughout a central portion as represented by reference character 8, but the width of the ward each end from the central section alon curves9 and 10. resistance element coinprising turns of wire 15 aregwound upon the band 4 in such manner that the turns of le the gradient adjacent each end of the potentiometer and in accordance with a di'erent law intermediate the ends.

Other and further objects of the inventhe ed e o the band 4. The contact is setion will be understood from the following a hub portion 17 to a shaft 18 specification by reference to the accompanywhich ma be rotated by means of knob 20 lie contact in moving over the cenrtion of the band 4 varies the resisty ance 1n relatively large and equal increments embodied; Fig. 2 is a front throughout the length potentiometer construcg'on whereas in sweeping over the turns throughillustrated in Fig. l; Fig. 3 iS a Side ele 9.-y out the length of the curved portions 9 and tion of the potentiometer construction shown 10 gradually .decreasing vincrements of re- 1; Fig. 4 is a plan view of a modisistance are obtained,'the increment chan e or m of potentiometer 'constructed in decreasing as the contact moves toward each accordance with my invention; Fig. 5 isa variab e contact i re l is a plan view of one form in tr'al whic the potentiometer construction of, m

invention may be end of the band 4. front elevation of the modified construction In Fig. 4 the band 6 Vis substantially cirshown in Fig. 4; Fig. 6 is a side elevation cular and is secured in position b binding of the potentiometer construction illustrated in Fig. 4; Fig. 7 is an elementary diagram showing the principle of construction of my potentiometer; Fig. 8 indicates the characteristic curves obtainable in an electrical cirposts 21 and 22 which ass throng the supporting member 23. 'Ilhe resistance' element 1s\\wound upon this band 6, the band being of substantial width throughout the'portion 24 and gradually diminishing in width near band gradually decreases to-l wire within the limits of thecentral section portion of the band to-` smaller of the portion 8,-

sweep over the turns, 15 on 30 moving contact 16 from one end 60v ance member, a variable 5 curves preferably follow a logarithmic law.

In Fig. 7 the principle of my invention is illustrated wherein the resistance coil -15 is of relatively largev width throughout a central portion and gradually decreases in Width toward each end following a logarithmic law represented by -curves 30 and 31. The variable contact 16 in moving along the resistance element is connected to any electrical circuit wherevariable potentials 15 are required. For example, as illustrated in Fig. 9, the potentiometer may be used for regulating the grid potential of electron tubes. In this diagram the radio receiving apparatus is illustrated employingan an- 20 tenna ground system 32, a tuned circuit 33,

and a two stage radio frequency amplifier 34, a detector 35, and a two stage audio frequency amplifier 36. Thegrid potential of the tubes forming the radio frequency amplifier 34 may be accurately regulated by use of my potentiometer indicated -at 15 having variable contact 16.l The opposite ends of the potentiometer being at opposite polarity permits a variation in grid potential by of the potentiometer to the other.

The characteristic curve in Fig. 8 repre- Asents the fine d egrees of potential variation obtainable in my potentiometer. As the contact 16 moves along the resistance 15 increments of resistance change are secured between plus, and minus potentials in accordance with a logarithmic law 37 and 38 adjacentl each end of the potentiometer while 40 within the central portion thereof the change follows a law represented by curve 39. It is of importance't-hat the grid potential variation near the positive and negative ends ot the potentiometer be quite accurate, par- 45 ticularly in operating tubes near negative grid potential where the-condition of oscillation must be very gradually approached. My potentiometer enables very small increment changes of potential to be secured.

W'hile I have described my invention in certain limited embodiments it is to be iindel-stood that my invention is not limited to the particular construction shown, but that various changes may be made within the scope of the appended claims without departing' from the spirit of my invention. What I claim and desire to secure by Letters Patent of the United States is:

1. A potentiometer comprising a'resistcontact for said resistance j member, being enlarged at a section intermediate the ends of said member and tapered from said intermediate section toward said ends.

2. A potentiometer comprising a resistance element, a variable contact for said resistance element, said resistance element having relatively large degreesv of adjustment adjacent a central section thereof and gradually decreasin' degrees of adjustment on each side of sai central section toward said ends. j f

3. A potentiometer comprising an insulated band, said band having a central portion and a gradually tapering portion at each side of said central portion, a resistance element carried by said band, and means whereby said variable contact sweeps over said resistance element including relatively large increments of adjustment within said central portion and relatively small increments of adjustment. within said tapered portion.

4. A potentiometer comprising a cylindrical band, a resistance wire carried by said resistance member said band. a variable Contact for said resistance wire along the edge of said band, said wire having relatively adjacent a central portion of said band and turns gradually decreasing in area toward each end of said band. A'

5. A potentiometer comprising an insulated band, a resistance Wire wound upon said band, a variable contact arran ed to sweep over said resistance element w ereby the value of said resistance varies according to a straight line law within one portion of said band and a logarithmic law on each side ofsaid portion. i j

6. A potentiometer comprising in combination an insulated band having one edge contained in the same plane and the opposite edge curved in accordance with a logarithmic law, ,a resistance wire carried on said band and a variable contact arranged to sweep over said wire on said first mentioned edge. Y

7. A potentiometer comprising in combination an insulated band having one edge contained in the same plane and the opposite edge oppositely curved from each end thereof in accordance with a logarithmic law, a resistance Wire\carried' on 'said band and a variable contact 'arranged to sweep over said wire whereby the increments of resistance change throughout said curves become increasinglyl large as said contact approxi- 'mates a position between said curves.

HoY'r s'. scofr'r.

large area turns 

